Made from defatted soya beans fermented with salt, water and crushed barley or wheat, soy sauce (or soya sauce) forms a basic ingredient in Japanese, Chinese and other Asian cooking. It's either added to dishes during cooking or used as a table condiment. There are many varieties of soy sauce that vary in consistency and in strength of flavour.
Light soy sauce is quite thin and has a saltier flavour than dark soy. It's used to give flavour to dishes without darkening them, such as when stir frying vegetables or chicken, for instance. Dark soy is thicker in consistency and richer. It gives good colour to noodle dishes and its sweetness makes it a good dipping sauce.
The darkest and richest is Indonesian ketjap (or kecap), which is made from black soya beans. Tamari is a dark soy sauce that's made without wheat, and is therefore suitable for coeliacs. Soy sauce is a versatile store cupboard ingredient. It makes a great marinade or it can be splashed into stews or used in sauces for meat and vegetables.